1. Technical Field
This invention relates generally to procedures and equipment for stopping an existing water, sewer, gas, or other line containing fluid under pressure, and more particularly to a valve assembly and installation method for inserting a valve in a line without otherwise shutting down the line during the insertion.
2. Description of Related Art
The task of inserting a valve in a line containing fluid under pressure (e.g., a municipal water line or natural gas line) without otherwise shutting down the line during the insertion can be expensive, inconvenient, and time consuming. Yet the need to do so is commonplace. Damaged fire hydrants, for example, frequently need replacement and doing so quickly in a cost-effective manner often involves shutting down water service while a valve is inserted in a water line branch feeding the fire hydrant.
One existing way of inserting a valve into a fire hydrant water line or other line without shutting down service proceeds by cutting a hole in the pipe with a known type of hot-tapping hole saw apparatus. A valving apparatus is then added that forces a rubber plunger into the hole. The rubber plunger expands enough to block the line. Withdrawing the plunger unblocks the line.
One problem with the rubber plunger technique is that success of the valving apparatus depends on the internal size and condition of the pipe. In addition, an old, corroded or otherwise damaged and weakened pipe is subject to being broken. Furthermore, pushing a plug through a tapped hole subjects the rubber gate to being cut by the sharp edges of the hole cut in the pipe each time the gate is opened and closed. For those and other reasons that will become more apparent, users need a better way to insert a valve in a water line or other line containing fluid under pressure.
This invention addresses the concerns outlined above by providing a valve assembly and installation method that function independent of internal size and condition of the existing pipe. A first subassembly (a valve body that assembles over the pipe) includes a bonnet-supporting flange that defines an access opening. A section of the pipe is cut and removed through the access opening to form a gate-receiving gap in the pipe that completely separates the pipe in separate sections. A second subassembly (a bonnet) is then mounted on the bonnet-supporting flange in the access opening where it operates to advance a gate through the gate-receiving gap in the pipe and into fluid-tight sealing engagement of the valve body. Thus, the condition of the pipe does not affect the seal.
To paraphrase some of the more precise language appearing in the claims and introduce the nomenclature used, the invention provides a valve assembly for insertion in a line formed by an existing pipe containing fluid under pressure. The valve assembly includes a first subassembly that forms a valve body and a second subassembly that forms a bonnet. The valve body has opposite first and second ends, a valve body axis extending between the first and second ends, and a bonnet-supporting flange intermediate the first and second ends that defines an access opening facing radially away from the valve body axis. The valve body is adapted to be assembled over the existing pipe so that the pipe extends along the valve body axis between the first and second ends of the valve body and so that a user or other installer can access the pipe within the valve body through the access opening for purposes of cutting and removing a section of the existing pipe in order to form a gate-receiving gap in the pipe.
The bonnet includes a gate and the bonnet is adapted to function as means for moving the gate through the access opening into the valve body, between an open position of the gate in which the first and second ends of the valve body are in fluid communication, and a closed position of the gate in which the gate extends through the gate-receiving gap in the pipe and into fluid-tight engagement of the valve body so that the first and second ends of the valve body are not in fluid communication. The flange-mating portion of the bonnet defines a gate opening through which the gate extends from the bonnet in a fluid-tight fit, and the flange-mating portion of the bonnet fits into the access opening in a fluid-tight fit. That arrangement enables a user to mount the bonnet on the valve body through a temporary isolation valve mounted on the bonnet-supporting flange in order to thereby facilitate insertion of the valve assembly when the existing pipe contains fluid under pressure.
In line with the above, a method of inserting a valve in a line having an existing pipe includes the step of providing the valve body subassembly and the bonnet subassembly described above, together with a temporary isolation valve, pipe-cutting means, and bonnet-mounting means. The method proceeds by (i) assembling the valve body over the existing pipe, (ii) mounting a temporary isolation valve on the bonnet-supporting flange, (iii) cutting and removing a section of the existing pipe through the isolation valve to form the gate-receiving gap in the pipe (iv) installing the bonnet through the isolation valve, and then (v) removing the isolation value up over the bonnet.
Thus, the invention overcomes problems associated with some existing techniques for inserting a valve in a line with a valve assembly and installation method that significantly facilitate the process. The following illustrative drawings and detailed description make the foregoing and other objects, features, and advantages of the invention more apparent.